The objectives of this research are to determine the number, size and other characteristics of the major virion proteins of measles and canine distemper viruses. These proteins will be compared with each other and with the proteins found in certain well characterized Paramyxovirus virions, such as SV5, Sendai and Newcastle disease. The measles and canine distemper viruses will be grown in Vero or AV3 cells. Virus will be labeled with H3 or C14-amino acid mixtures. Labeled virions will be purified by a combination of discontinuous and continuous sucrose density centrifugation and analyzed by SDS gel electrophoresis. The proteins from two different viruses will be compared by co-electrophoresis. Glycoproteins will be identified by co- electrophoresis of H3-glucosamine and/ or H3-fucose labeled virions with C14-amino acid labeled virions. Nucleocapsid proteins will be identified by co-electrophoresing dissociated nucleocapsid isolated and purified from infected cells or virions with whole virion proteins. The dissociated virion proteins will also be characterized by isoelectric focusing. Attempts will be made to identify and isolate biologically active cell fusion proteins from measles and canine distemper virions and/or infected cell membranes. Attempts will also be made to identify and/or isolate measles hemagglutinin.